Semireentrant line oscillator for ultra high frequency, comprising an electron discharge device



March 22, 1949. s. LOBEL 2,464,984

' SEMIREENTHANT LINE OSCILLATOR FOR ULTRA HIGH FREQUENCY COMPRISING AN ELECTRON DISCHARGE DEVICE Filed Oct. 8, 1945' 5 2 22 5 26 INVENTOR.

N 22 I I SEYMOUR LOBEL BY 8 v ATTORNEYS Patented Mar. 22, 1949 SEMIREENTRANT LINE OSCILLATOR FOR ULTRA HIGH FREQUENCY, COMPRISING AN ELECTRON DISCHARGE DEVICE Seymour Lobel, Brooklyn, N. Y., assignor to Air King Products Compan New York y, Inc., a corporation of Application October 8, 1945, Serial No. 621,065

7 6 Claims.

This invention relates to high-frequency oscillators and particularly to oscillators. designed to operate at very high frequencies of the order of 1000 mc.

In the design of oscillators for operation at progressively higher frequencies, it was early proposed to utilize the resonant properties of a concentric-conductor transmission line as the frequency-determining element of the oscillator. In such an arrangement, the frequency of the oscillator is adjusted by varying the effective length of the line either by an adjustable shorting disc or ring, or by relatively telescoping the inner and outer sections of the line. However, even at very high frequencies the physical dimensions of such a line designed for frequencies generally encountered and adjustable over reasonable frequency ranges become unsatisfactorily large, .resulting in a number of disadvantages in addition. to the bulk of the apparatus itself. In the first place there arises the difilculty in connecting such high-frequency oscillators, such concentric transmission lines have been designed as reentrant lines, that is each end of the line has been effectively folded back on itself concentrically or telescoped. Such a configuration has certain of the characteristics of an oscillating cavity and it is not clear Whether the resultant oscillations are in the mode of a cavity oscillator or that of a transmission-line tuned oscillator.

provide a desired wide range of tuning" at very high frequencies, the low frequency end of the? tuning range, corresponding to the fully telescoped reentrant portions of the transmission line, is often below the desired minimum fre-T quency. On the other hand, it would be desirable to provide an oscillator of the type described in which the lower limit on the tuning range is' materially raised.

It is an object of the invention, therefore, t

provide a new and improved oscillator of the type described which is capable of operating overa However, it has been found that in such reentrant-line osc il.-i lators if the physical dimensions'are such as to relatively wide frequency range in which the lower limit of the range is materially raised while. maintaining the maximum physical dimensions of the apparatus within reasonable limits.

It is another object of the invention to provide a new and improved oscillator of the type described in which the tuning range is spread over a wide range of adjustment of the tuning elements, thus facilitating the tuning operation.

It is another object of the invention to provide a new and improved oscillator of the type described having a maximum frequency stability, that is a minimum frequency drift.

In accordance with the invention, the oscillator is of the semi-reentrant-line type and com-I prises an electron discharge device having anode, cathode and grid electrodes, a hollow closed transmission-line conductor extending from one of the electrodes and an external terminal member extending from another of the electrodes and disposed coaxially within the conductor. The oscillator also includes a non-reentrant terminal member engaging the electrode terminal and extending substantially across the conductor and having a concave surface disposed toward the remote end thereof and a telescoping plug coaxially mounted in the remote end of the conductor and axially adjustable with respect to said concave surface to tune the oscillator. By the term "semireentrant line as used herein and in the appended claims is meant a line in which only one end of the line has been effectively folded back on itself or made reentrant, as distinguished from the fully reentrant lines described above in which both ends are made reentrant.

For a better understanding of the invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings, while its scope will be pointed out in the appended claims.

Referring now to the drawings Fig. 1 is a view, partly in cross-section, of an oscillator construction embodying the invention and showing. schematically the associated electrical circuit; connections; Fig. 2 is a top view of the grid ter'-. minal member embodied in the oscillator of Fig. 1; while Figs. 3a and 3b are top and side views, respectively, of a modified form of grid terminal member.

Referring now to Fig. 1 of the drawing, there is shown a semi-reentrant-line oscillator em-. bodying the invention. This oscillator comprises an electron discharge device or vacuum tube l0 having an anode electrode Illa, a cathode electrode i012 and a grid electrode I 00. While the vacuum tube Il] may be of any suitable type, there is illustrated a construction corresponding to the type 3037 in which the anode Ilia is in the form of an annular external conductive member which divides the envelope into two portions Id and, We and is sealed to such portions at the junction. The cathode Illb is in the conventional form of a hollow sleeve coated with electron-emissive material and provided with an internal. heater IOf brought out to conductors IIIg through a seal. "lb. The cathode Iflb is supported from the seal Illh by rods or posts I61, the seal IIIh and cathode IIlb being electrically connected to one of'the heater leads Illg, as indicated. The grid Illc is in the form of a cylindrical cage mounted on a post I09 extending through the lower envelope portion I02 and including an external cylindrical heat-radiating terminal Illlc comprising a series of circular radiating discs or fins surrounding the post I09 and having a terminal face IIlm normal to its axis.

The oscillator also includes a hollow closed. transmission-line conductor extending from the anode. annular member Ifla. This conductor may be. in the form of a cylindrical sleeve II surrounding and coaxial with the vacuum tube ID and electrically connected to the anode member llla by means of a connection plate I2 having a plurality of resilient radially inwardly extending. fingers contacting the member Illa and soldered. or otherwise electrically bonded to the cylinder. I I about its. periphery. Thevacuum tube In may be. supported by means of its annular anodemember. IBa ona disc I3 of heat radiating material,v

such as copper, soldered, brazed or otherwise secured in the cylinder II. The lower end of the cylinder II is closed in. any suitable fashion as by a conductive cup-shaped member I4 soldered or. otherwise electrically bonded about its meriphery to the cylinder II. In the upper end. of the. cylinder. II isdisposed a telescopically sliding. cup-shaped conductive cathode-tuning member. I5. spaced from thecylinder II by meansofla plurality of spacers I6 of insulation material and electrically connected to the cathode-I01), as indicated. With the construction. described, the heateradiating grid terminal IIlk is disposed coaxially within the transmission-line conductor I I.

The oscillator also includes a non-reentrant terminal member I! engaging the grid terminal, III]: and extending substantially across the cylindrical conductor I I and having a concave surface. disposed toward the remote end thereof. The member I'I, shown in plan View in Fig. 2, may be in the form ofa cup-shapedmember of resilient conductive material, such as a beryllium-copper alloy, and includes a plurality of radially inwardly extending resilient fingers I Ia,.preferably curved slightly upwardly andengagingthe. terminal face IIlm of the gridterminal IIllc. An annular spacer I8 of insulation material is in.- terposed. between. the. rim of the. terminal memeb'er I I and. the cylindrical conductor I I .and'serves. to. support the. member. I! within the. conductor. II and to form therewith one end of an anodegrid oscillation cavity.

In order to tune the oscillator over a desired? range of frequencies, there is provided a telescoping plug I9, preferably in the form of;.a hollow-cup-shaped member coaxially mounted in. the'end plate I I of the conductor II. and axially adjustable to tune theoscillator. The telescoping plug I9 may be. supported mechanically. in any suitable manner, not shown. Electrical'eonnectlon is maintained between the cylindrical conductor I I and the plug I9 by a plurality of resilient radially inwardly extending fingers Ila upset from the terminal cup I5 and resiliently engaging the periphery of the telescoping plug I9.

One circuit arrangement for making external electrical connections to the oscillator of the invention is illustrated schematically in Fig. l of the drawings. The transmission-line conductor II is connected directly to ground and to a suitable s0urce+B of space current. The negative terminal'of the space current source -B is connected by way of one of the heater conductors lllbtto the cathode seal H172. and cathode lb. The cathode heater IN is energized from any suitable source of alternating current by way of supply circuit terminals 20 and an isolating transformer 2|. The oscillator described is particularly suitable for operation at peak power outputs by pulsing control. To this end, there are provided pulse-circuit supplyterminals 22 connected to the grid lll'cbyway of. an isolating transformer 23,

a grid resistor 24, a' filter 25 comprising a series inductanceelement 25a and a shunt condenser 25b,",a conductor 2.1, and the grid heat-radiating terminal I 076.. A suitable bias potential on the gridlis established by connecting the cathode I III) to the grid through a radio-frequency choke coil 26Jand agrid'resistor 24, the cathode, and thus the source. B, bein by-passed to ground for radio frequenciesby a condenser 28. High-frequency output oscillations may be derived by' means. of'a single-turn. pick-up coil 29 extending through andinsulated from the. cylindrical conductor II and extending into the grid-anode oscillation cavity. The pick-up coil 29 is connected toone of'the.outputlterminals30, the other one of which is grounded. As indicated by the dotted- Y lineresonant circuit 3I, the grid-anode cavities formed between the grid terminal I Ok, the member I1 and the transmissioneline conductor II is the equivalent of a frequency-determining resonant" circuit 3.I. the cylinder II between the anode member Illa and the. cathodeetuning cup I5 forms an anodecathode oscillation. cavity'which is the equivalent.of and represented by the dotted-line resonant circuit 32.

It is believed that the operation of the oscillator of the invention will be apparent to those skilled in the art from the foregoing description. Essentially, the oscillator is a conventional one in which thefrequency-determining element represent'edb'y the equivalent tuned circuit 3I is connected between the grid and anode of the oscillater and serves both as the frequency-determim ing element and the. regenerative feedback coupling from the anode circuit to the grid circuit. The frequency of the oscillator is determined by the dimensions of the grid-,anode cavities. There are two of these cavities, one bounded by the anodemember Illa, the cylinder II and the grid terminalmernber I! and the other formed by the' grid? terminal member. I 'I, the anode cylindrical conductor II, andthereentrant plug I9. The

Similarly, the upper end of This latter cavity may be enon within this cavity is not precisely understood, since the construction is somewhat of a hybrid between a concentric transmission-line tuner, composed of the outer cylindrical conductor H and the inner cylindrical conductor made up of the grid post I09, the grid terminal I070 and the terminal member I! and having a reentrant portion formed by the plug H! at one end, and that of the more conventional simple cavity oscillator formed by the cavity between the grid terminal member I! and the end plate 14 of the cylindrical conductor 1 l as modified by the position of the tuning plug l9. In any event, these elements together constitute an oscillation or frequency-determining assembly, the frequency of which may be adjusted over a relatively wide range by axial adjustment of the plug I9.

As indicated, the cathode tuning cup I 5 with the upper portion of the cylinder H forms an oscillation cavity equivalent of the parallel resonant circuit 32. The natural frequency of this cathode cavity has a broad effect on the oscillator frequency and its power output. The adjustment of the tuning cup i5 is preferably preselected to favor the oscillator eificiency at the higher frequencies of the tuning range, at which it otherwise tends to fall off, and the cup is then fixed in this position.

The cavity between the grid terminal I! and the anode member Ella also constitutes a fixedfrequency oscillation cavity. If the end cup M, the tuning plug l9 and the lower end of the sleeve H were removed, the frequency of the oscillator would be determined by this cavity. The effect of the addition of the adjustable cavity including the tuning plug I9 is to lower the mean frequency of the oscillator. In other words, the oscillation frequency of the cavity above the grid terminal member ll is the limiting factor on the highest frequency of the tuning range.

As stated above, the oscillator described is one particularly suitable for pulse control. To this end, a pulse signal, such as represented by curve A adjacent to terminals 22, is applied to these terminals, thence through the transformer 23, the grid resistor 24 and the filter circuit 25 to the grid terminal Hlk. With this arrangement, the apparatus is effective to develop oscillations only during the negative pulses of curve A. During intervening periods, the bias on the grid I00 is such as to prevent oscillation. There is thus derived from the output terminals 30 a series of pulses or trains of very-high-frequency oscillations having a modulation envelope represented by curve A.

In Figs. 3a and 3b are represented a modified construction of grid terminal element H1 having a plurality of resilient radially inwardly extending contact fingers Hal. It has been found that this construction operates in a manner substantially similar to that of the grid terminal member ll of Fig. l but, due to its slightly different configuration, the tuning range of the oscillator embodying this element is somewhat less than that of Fig. 1'.

While the physical and electrical dimensions and constants of the oscillator of the invention obviously Will vary within wide limits in accordance with the tuning range, the mean frequency of the range, and other performance characteristics desired, there follow, by way of example, the more important dimensions and constants of a particular oscillator embodying the invention, the physical dimensions being expressed in terms of the wave length of the generated oscillations:

Tube 10 Type 3C3? Cylindrical conductor 11:

Diameter 0.237 Length 0.700 Grid terminal member 17:

Diameter 0.162 Length 0.056 Tuning plug 19:

Diameter 0.106 Length. 0.200 Range of penetration into. cavity oscillator 0050-0112 Cathode tuning cup 15: Diameter 0.187 Length 0.250

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.

I claim:

1. A semi-reentrantline oscillator comprising, an electron discharge device having anode, cathode and grid electrodes, a hollow closed transmission-line conductor extending from a first of said electrodes, an external terminal extending from a second of said electrodes and disposed coaXially within said conductor, a non-reentrant terminal member engaging said terminal and extending substantially across said conductor and having a concave surface disposed toward the end thereof remote from said first of said electrodes, and a telescoping plug coaxially mounted in said remote end of said conductor and axially adjustable with respect to said concave surface to tune said oscillator.

2. A semi-reentrant-line oscillator comprising, an electron discharge device having cathode and grid electrodes and an anode including an annular external conductive member, a hollow closed transmission-line conductor extending from said anode annular member, an external terminal extending from said grid electrode and disposed coaxially within said conductor, a non-reentrant terminal member engaging said terminal and extending substantially across said conductor and having a concave surface disposed toward the end thereof remote from said first of said electrodes, and a telescoping plug coaxially mounted in said remote end of said conductor and axially adjustable with respect to said concave surface to tune said oscillator.

3. A semi-reentrant-line oscillator comprising, an electron discharge device having anode, cathode and grid electrodes, a hollow closed transmission-line conductor extending from a first of said electrodes, a cylindrical heat-radiating terminal extending from a second of said electrodes externally of said device and disposed coaxially within said conductor, a non-reentrant terminal member engaging said terminal and extending substantially across said conductor and having a concave surface disposed toward the end thereof remote from said first of said electrodes, and a telescoping plug coaxially mounted in said remote end of said conductor and axially adjustable to tune said oscillator.

4. A semi-reentrant-line oscillator comprising, an electron discharge device having anode, cathode and grid electrodes, a hollow closed transmission-line conductor extending from a first of said electrodes, a cylindrical heat-radiating terminal extending from a second of said electrodes anemone;

externally; of said device and disposed coaxially:

within said conductor and having a terminal face normal to its axis, a non-reentrant terminal member including a-plurality of resilient fingers engaging said terminal face and extending substantially across said conductor and having a concave surface disposed toward the end thereof remote from said first of said electrodes, and a telescoping plug coaxiallymounted in said remote end'of said conductor andaxially adjustable to tune said oscillator.

A semi-reentrant-line oscillator comprising, an electron discharge device having anode, cathode and grid electrodes, ahollow closed transmission-line conductor extending from a first of said electrodes, a cylindrical heat-radiating terminal extending from a secondof said electrodes externally of said device and disposed coaxially within said conductor and having a face normal to its axis, a non-reentrant terminal member comprising a cup-shaped member of resilient conductive material including a plurality of radially inwardly extending resilient fingers engaging said terminal face and extending substantially across said conductor and having its concave surface disposed toward the end thereof remote from said first of said electrodes, and a telescoping plug coaxially mounted in said remote end of said conductor and axially adjustable to tune said oscillator.

6. A semi-reentrant-line. oscillator comprising,

81 an-zelectron' dischargedeviceihaving anode; catin ode and grid electrodes; a:- hollow' closed-transemission-line conductor extending from i a' first: oti said electrodes;v a terminal extending from: a; second of said electrodes externally of'saidj de vice anddisposed coaxially within said conductor; a non-reentrant terminal member engaging said, terminal and extending substantially across said: conductor and having a concave surface disposed toward the end thereof remote from said; first of said electrodes, insulation spacing mean-sir. interposed between the periphery-of said mermber and said conductor and forming therewitbi one closure of said hollow closed conductor, and.;. a telescoping plug coaxially mounted in said re'-- mote .end of said conductor and axially adjustable; to tune said oscillator:

SEYMOUR'LOBEL- REFERENCES CITED 'The following references are of record in thefile of this patent:

UNITED STATES PATENTS Number Name Date 2,167,201 Dallenbach July 25, 1939 2,169,396 Samuel Aug. 15, 1939' 2,207,846 Wolff July 16, 1940" 2,400,753 Haeif May 21, 1946 2,408,355 Turner Sept. 24, 1946 2,412,997 Litton Dec. 24, 1946'- 

